Infusion apparatus



B. B. HOLMES INFUSION APPARATUS Filed Sept. 13. 1939 BY @m94 ATTORNEYS.

Patente-d May 7, 1940 UNITED vSTATES param OFFICE 2 Claims.

This invention relates `to domestic cooking vessels, and particularly topots'for making infusions of coiee. 1

In the past, four distinct methods of 'preparing coiee have been incommon use. Ordinary boiled coffee is well-known, and is generallyconsidered objectionable because boiling of the infusion impairs theflavor. The so-called percolatormeth od, in which a flash vsteampocketis used to .return 10. small quantities of the infusion above thelter bed is even more objectionable because the nfu sion is boiled andbecause inaccessible surfaces become coated with substances extractedfrom the colee. These substances become rancid a-nd 1,5- scmetimesburned and thus impair the flavor of the infusion.

For many years the French drip method was considered to produce the bestc'oee. According to this method, water, at a boilingztemperature, isfiltered by gravity through a, bed of ground coffee, making usually asingle pass to produce the desired infusion. Experts agree that `this is'one of the best Ways to prepare coffee, but in the hands ofthe averageuser, the results are 'not uni- 25 form. A common 'cause of ,failure isthe' use of Water which is not strictly at the boiling temperature.Furthermore, part of the water cools before it can all pass the ."lter,and the vtime afforded 'for infusion 'is not controllable becausecloverthe colee, and there can be no y'definite time period that the Water andthe ground coffee are held in Contact prior to the inception .of vthefiltering step.

sive use in the last twenty years. is the pressure vacuum transfermethod making` use of a heat resisting glass flask and a heat resisting'glass funnel tube sealed together. This scheme allows control oftheinfusion time but is subject to 4'definite objections. These potsfilter rather slowly and many of them require the use of an.objectionable lter cloth. The chief objection, however, is that if thepot be left on the stove after the water has 45 been displaced upwardinto the funnel Aso as to extend the period of infusion, steam continuesto pass upward through the water mixed with ground coiee and byimparting kheat thereto keeps'the water actively boiling. This has in asomewhat 50 less marked degree the same harmful .eiect that isencountered in making boiled coffee. Such boiling can be prevented byremoving the pot immediately from the stove once the Water hasrisen, butv`the immediate descent of the infusion which results prevents the useof thevoptimum time vfor tering flow starts as soon as the 'Waterispoured The fourth method whichhas come into exteninfusion. Moreover, theduration of the descent is aiected .bythe flneness of grind of thecoffee, for the reason that the coffee itself forms the principal.filtering bed and the area of flovvfrom the `upper bell or container islimited to the relatively smal-l area of the tubular neck. Obviously,this small area intensifies .the effect .of the neness of grind on .thetime required-.for filtration.

:The purpose of the present inventionis to combine .ina simple.structure .the .best features ofthe drip process and the kpressurevacuum infusion process while avoiding the defects characteristic ofeach. The features so combined are (1) gravity ltrationlon ailter bed oflarge area vand relatively shall-ow .depth (characteristic of the Frenchd-.rip method); .(2) possible retention yof boiling water on thecoffeegrounds for a definite :period priorto the initiation of the .filteringstep (characteristic of the pressure-vacuum transfer lsystem), and (.3)assurance that the Water delivered to the .coifeecgrounds will be atboiling temperature (as is the ycase in the pressure-vacuum transiersystem) and will not rbe boiled 'after it is delivered .to the vgroundcoffee (which isa feature characteristic of the .Frenchdrip method).This gives the user control of factors which determine the nal result toan extent not heretofore Vattained. f

The device A:consists of three essential parts of very simple form: apot so shaped that it is sim- 3.0 ple to `manufacture and easy to keep4absolutely clean, a steam .bell of equally simple form, and a coieecontainer which is simply a cup-shaped member with an annularlycorrugated bottom having perforations through the troughs of thecorrugations.

It is preferred to use a retainer and Water distributing plate which issimply a perforated anged disk designed to overlie the coffee in thecoffee container, but this can be omitted.

A cover for the complete assembly would ordinarily be provided, but hasno functional significance.

The construction of the device is such that if extremely clear coiee isdesired, a filter disc of clcthor paper or a very fine mesh screenmaterial may be laid in .the bottom of the coffee container, but sincethese expedients are well-'known and do not aiect the oper-ation of theinvention here .described except as rthey perform a knovvn filteringfunction, vit is not deemed necessary to illustrate the optional use ofthese refinements.

.In order that the importance of certain details in .construction may beappreciated as the description proceeds, the general operativecharacteristics will be outlined. The pot is so constructed that wateris brought to a boil in the lower half of the pot while the coifeegrounds are held in the vcoffee container above the water level.

A steam bell functions to do two things: As soon as steam is generated,that is as soon as the water comes to a boil, the steam bell rises andacts as a valve to protect the coffee grounds from the upward passage ofsteam or water. The development of steam pressure within the bellfunctions to displace nearly all the water from the lower portion of thepot to entrance ports around the coffee container near the top thereof.So long as the water in the bottom of the pot is kept at a boil, thewater in the coee container can not descend and no steam generated canpass upward through the infusion then being made in the coffeecontainer. However, the discharging steam does flow around and incontact with the periphery of the coffee container and without impartingmuch heat to the coffee container, serves as an isolating envelope whichprevents loss of heat.

Thus, the time of infusion may be chosen at will without risk that theinfusion while being made. will either boil or fall appreciably belowthe boiling temperature.

When the heat is turned off, the condensation of steam beneath the bellpermits the bell to descend and then the infusion filters through thecoffee bed under gravity, exactly as it would in a French drip potexcept that the infusion is certain to be just below the boiling point.

An important detail of construction is the provision of a depression inthe top of the steam bell which keeps the discharge openings in thebottom of the coffee container slightly submerged in a bath of liquidinfusion during the filtering operation. This detail assumesconsiderable importance near the end of the filtering operation for thereason that when the liquid head on the minute drain openings is of theorder of 1/8th inch, a capillary or surface tension effect will inhibitow unless the orifices are submerged. This detail thus permits morecompleted drainage of the filter than can otherwise be attained.

A preferred embodiment of the invention will now be described withreference to the accompanying drawing in which:

Figure 1 is a plan View of the pot with cover removed and with half ofthe distributor plate broken away to show the form of the bottom of thecoffee container.

Figure 2 is a vertical axial section through the complete pot with thesteam bell in its initial or lower position.

Figure 3 is a fragmentary view similar to a portion of Figure 2 butshowing the steam bell in the upper position which it assumes after thegeneration of steam commences.

Referring particularly to Figures 1 and 2, the pot comprises acylindrical shell 6 with a bottom which, if desired, may be recessed asindicated at l, although a flat bottom may be used.

While any type of spout might be provided, I prefer simply to strike outa flaring spout from the side wall of the pot Il, as indicated at 8.This is shown diametrically opposite the handle 9 which is of insulatingmaterial and attached to the side wall of the pot in any suitablemanner.

Positioned in the lower portion of the pot and occupying perhaps thelower 2/5 of its vertical extent is a steam bell II. This is simply aninverted cup whose external diameter is about one-eighth inch less thanthe internal diameter of the pot. Te lower margin is preferablyreinforced with a bead I2 and the closed top is dished to provide aperipheral rim I3 which encircles a depression or basin indicated at I4.

The rim I3 performs a valve function and the basin I4 retains a portionof the coffee infusion during the filtering operation, as will beexplained.

Slightly below the crest of the rim I3 and outside the same is a minutevent port I5. It will be observed that the entire bell structure issimple in form, economical to manufacture and so accessible that it canbe kept perfectly clean.

The coffee container I6 is a cylindrical, opentopped cup whose externaldiameter is approximately that of the bell II and whose upper end isbeaded as indicated at II to define the position of the container in thepot and to stiffen the rim. The vertical dimension of the container issuch that the peripheral shoulder I8 at its lower end is spaced a shortdistance above the rim I3 on the steam bell II, when the steam bellrests on the bottom of the pot 6.

The bottom of the coffee container I6 is provided with a series ofconcentric annular corrugations I9 formed in a portion of the pot struckdown from the plane of the shoulder I8. Whenthe bell II rises and causesits rim I3 to seat on the shoulder I8, the corrugations I9 are receivedin the basin I4. When the bell settles, they are still slightly belowthe top of the rim I3. A series of minute perforations 20 are provided,preferably in the bottoms of the corrugations I 9. One purpose of solocating the perforations is to permit the use of a disc of lter paperor a disc of cloth, or a fine mesh screen disc laid over thecorrugations to perform a well-known auxiliary filtering function, incase the user desires this refinement. This is by no means necessary,and since the use of such filters is a common expedient, no filter isillustrated in the drawing. The use of a filter is no part of theclaimed invention, but the invention does not exclude the use o-f afilter.

To prevent the coffee container I6 from fioating upward when the `hotwater rises, some latching means must be provided and an ordinary springdetent is indicated at 2|. This is shown mounted on top of handle 9 butany known means for latching or locking the cup I6 may be used. l

Encircling the coffee container I6 near its upper margin is a series ofrelatively large perforations 22. These may completely encircle thecoffee container, but I prefer to omit them opposite the spout 8. Theperforations 22 are suciently large and sufficiently numerous to draininto the coffee container I6 al1 water which rises between the containerand the pot 6 when the water boils. Otherwise the water would overflowthe pot.

When no strainer disc is used in the bottom of the coiee container I6,it is desirable to prevent the water cascading through the perforations22 from stirring up the ground coffee. Consequently, I use a perforateddisc 23 which rests upon the coffee in the coifee container. It isprovided with a knob 24 by which it may be lifted out, and a peripheralflange 25 of moderate height.

The purpose of this ange is to serve as an impositive retaining meansfor the disc 23. The

coffee infusion may be poured from the pot with- 75 out removing any ofthe parts and when this is done, the tilting of the pot may cause thedisc 23 to cant slightly. Its cooking action causes the ange to lock thedisc against further movement,

I prefer to provide a cover 26 with a knob 21. This is simply a angedcover of familiar form. It is notched to clear the latch 2| as indicatedin Figure 2.

To make coffee, the pot is lled with water to about the line A-A. Theinverted bell II is then dropped into the pot and because the port I5vents the air Within the bell, the bell settles to the bottom of thepot, assuming the position shown in Figure 2.

The coffee container I6 is filled with suitably ground coffee asindicated at B. The coffee is leveled off and the disc 23 is placed uponits top. The container I6 is then inserted into the top of the pot andlatched in position, as shown in Figure 2.

If a filter disc of any type is placed in the bottom of the coffeecontainer I6 beneath the coffee, the disc 23 may be omitted becausequiescence of the coffee grounds is not then important.

Some users prefer the use of a filter disc and the omission of theoverlying disc 23 because it then is practicable to stir the coffeewhile the infusion is being made.

The water in the pot is then brought to a boil. Shortly before the waterboils, a small amount of occluded air will be driven off from the waterand escape through port I5. When the generation of steam exceeds thecapacity of port I5, the bell II will rise and the rim I3 will seatagainst shoulder I8 so that neither steam nor water can flow in anysubstantial quantity upward through the perforations 20 (see Figure 3).However, the steam trapped beneath the bell II displaces water from thebell and causes it to iiow upward in the clearance between the bell I Iand the container I6 on the one hand, and the vertical Wall of the pot6. When the water reaches the perforations 22, it cascades through theseperforations into the container I6 and is distributed by the perforateddisc 23 evenly over the entire bed of coffee.

It will be observed that water will remain in the bottom of the pot'to adepth of a fraction of an inch. All the rest of the water originallycontained in the lower part of the pot is transferred to the containerI6, the depth being indicated by the line C-C in Figur-e 2. So long asthe water in the bottom of the pot is kept boiling the bell II willremain in its upper position. Consequently, no ow tends to occur fromthe coffee container I6. Thus'the forming infusion remains in thecontainer I6 and is kept hot, but not boiled, by steam owing through theclearance between the pot Wall and the wall of the container I6.

After an appropriate time interval, the pot is removed from the stove orthe stove is turned off. The escape of steam through port I5 andcondensation of steam beneath the bell II allow the bell to descend andimmediately gravity draining of the infusion occurs. The basin I4retains a bath of coffee infusion on the perforations 20 and thusinsures complete vgravity flo-w from the container I6 by inhibitingsurface tension effects on the minute holes 2l). While the device willoperate without the submerging basin I4, tests have shown that thismarkedly assists complete drainage of the coiee container.

Satisfactory filtering can be attained by using contact withr thegrounds in container I6 for a period of about three minutes, but theduration of this step is subject to the complete control of the user,and the draining time either with or Without filter discs is so shortthat the time of producing coffee compares favorably even with that ofthe glass coffee pots in which the filtering action is assisted by thevacuum effect.

The amount of coffee used and the nature of the grind andr similarcharacteristics which are are' often critical factors with other typesof pot are much less important with the pot herein described. Tests havedemonstrated that approximately uniform results can be had if the timeduration of the infusion operation is standardized. The fineness of thegrind of the coffee and, Within limits, the quantity used have lesseffect than with other types of pot, in which the time of infusion isnot controllable. This follows for the reason that the lter area islarge, the depth of ground coffee is comparatively small in any event,and gravity ltration does not result in compacting the coffee groundsinto a dense, relatively impermeable lter bed (such as is characteristicof the pressure-vacuum transfer method).

The quality of the coffee infusion prepared in pots of this type isuniform and excellent because the infusion is made practically atboiling temperature but under conditions which inhibit active boiling atany time. The duration of time within which infusion is made is underaccurate control of the user. All parts of the pot are accessible andcan veasily be kept scrupulously clean.

Since the essential oils present in coffee infusions tend to coat thecontainer and become rancid if allowed to remain, the accessibility ofall parts of the pot and the ease with which it may be kept clean areVital considerations.

While the components described can be made of various materials, theirsimplicity and the ease of cleaning makes it possible to use metalwithout entailing the objectionable results heretofore encountered withmetal pots.

While the invention has been described in considerable detail, thedescription and the illustration are exemplary and not limiting.

The scope of the invention will be dened solely in the claims.

What is claimed is:

1. In a device for preparing hot infusions of coffee, the combination ofa pot dimensioned to contain in its lower portion the entire charge ofwater to be boiled; a removable coffee container of somewhat smallerhorizontal dimension than said pot for containing a charge of coffee andprovided with lateral Water inlet ports` near its top and with bottomstraining perforations distributed over substantially the entire bottomexcept a marginal encircling sealing area: releasable means forretaining said container in the upper portion of the pot with the bottomof the container above the level of said water charge; and meanscomprising a bell substantially submerged in said charge in the pot, for

displacing the major portion of said water up- 75 ward around the belland between the container and the Walls of the pot to said inlet portsupon the generation of steam from the Water charge, said bell being freeto float upward and having a marginal portion which then engages saidsealing area to inhibit ow upward through said straining perforationswhile steam is being generated, whereby escaping steam is caused to owaround said container, said bell having a con- 10. stantly openrestricted vent.

